Polyolefine parts and foils with permanently improved surface properties

ABSTRACT

Polyolefine-based mouldings and foils contain internal bonding additives which are enriched by migration at the plastic surface and which have their molecular structure bonding substituents of higher polarity on an oleophilic hydrocarbon radical. At least one part of these internal additives is hardened via its hydrocarbon radicals in the area of the plastic surface and prevented from further migrating, and so permanent adhesive bondings and/or coatings of the polyolefine surface may be obtained without additional preliminary treatments. Also disclosed is a process for furnishing solid polyolefine surfaces with such adherence-improving, immobilised additive (mixtures), and other auxiliary agents used for that purpose.

BACKGROUND OF THE INVENTION

Molded workpieces of any three-dimensional form, including fibers andfilaments, and films based on polyolefins, more particularlypolyethylene and polypropylene, are used on a very wide scale inpractice. An important problem area here is improving the surfaceproperties of these structurally nonpolar hydrocarbon components. Thus,the inadequate adhesion of coatings, adhesives, printing inks and thelike is a central problem which has remained unsolved for decadesdespite numerous attempts to find a solution.

A comprehensive account of the various proposals which have been madewith a view to solving the stated problem can be found, for example, inEP 0 311 723. In the interests of simplicity, reference is hereby madeto the disclosure of this document.

The concept of improving adhesion to hard polyolefin surfaces in realityencompasses an extremely broad range of very different technicalrequirements. This will immediately become clear from the followingcomparison: improving the adhesion of a printing ink to polyolefin filmscannot be compared with improving the adhesive bonding to a rigidpolyolefin molding of solid workpieces of metal or other plastics withno risk of adhesive failure when mechanical forces are applied to thebond. Of considerable practical significance moreover is the dependenceon time of the adhesive strength established, the notion of dependenceon time in turn encompassing two different parameters. The firstconcerns the time interval elapsing between production of thepolyolefin-based molding and its subsequent coating or bonding. Thesecond quality parameter concerns maintenance of the adhesiveness valuesinitially established in the bonded workpiece or coated material overthe duration of its practical use which, as well known, can involve verylong periods of time, for example of several years. What is required inpractice for a number of applications of the technology under discussionhere is the possibility of establishing high-strength bonds by coatingand/or application of adhesives using standard auxiliaries up to andincluding resistance to adhesive failure with no dependence on timebetween production and finishing of the polyolefin-based molding on theone hand and its coating and/or bonding on the other hand, the strengthvalues once established remaining intact for virtually indefiniteperiods.

The teaching according to the invention starts out from this objective.In addition, the invention seeks to create the possibility of notnecessarily having to use past technical proposals for solving theproblem discussed in the foregoing. Thus, it is known that the adhesivestrength of polyolefin-based materials can be substantially increased byprocessing high molecular weight copolymers containing coupling polargroups in the polymer structure together with the nonpolar polyolefinand/or by imparting the permanent high polarity required to the nonpolarpolyolefin by grafting on polar elements, cf. for example thedisclosures of DE 34 90 656, EP 0 467 178 and JP 222 181.

Numerous proposals from the prior art are also concerned withincorporating comparatively low molecular weight mixture componentscontaining polar substituents in the polyolefin-based polymer. Theproposals in question are mainly concerned with improving the adhesionof, above all, printing inks to polyolefin films, i.e. with fulfilling arelatively moderate technical requirement. The following documents arecited purely by way of example as representative of the extensiveprior-art literature:

DE-OS 27 29 886, EP 0 402 100, U.S. Pat. Nos. 3,396,137, 5,286,525 and5,393,814 and JA 0 54 331. The cited documents are mainly concerned withimproving the adhesive strength of polyolefin films with respect to theapplication of printing inks. The use of known surface treatments, moreparticularly corona or plasma pretreatment, is also prescribed.

DD-PS 50 947 is concerned in its introduction with proposals toincorporate low molecular weight additives containing polar substituentsin polyolefin-based molding compositions. Reference is made here to theabove-mentioned fact that, where low molecular weight internal additivessuch as these are incorporated, the corresponding polyolefin moldingsshow decreasing strength values and hence deteriorations in theirmechanical properties after prolonged exposure to mechanical forces.

The reason for this unwanted development of the property spectrum ofcorrespondingly finished materials lies in the known migration of lowmolecular weight components containing polar substituents in admixturewith the polyolefin. Even if these low molecular weight additives areuniformly incorporated, the effect known as blooming-out occurs. Duringstorage of the polymeric molding containing low molecular weightcomponents or the corresponding film, the low molecular weight additivesmigrate outwards to the surfaces of the molding. Ultimately, even thehydrocarbon residues of the additives separate from their physicalmixture with the polyolefin substance. The additive then exists as aliquid or solid film on the polyolefin surface. This naturally has acritical influence on the increasing deterioration in the adhesionvalues in the corresponding composite material. For comparatively slightstressing, for example the printing of polyolefin films, the immediateresult does not have to be technical uselessness, especially since otherproperties of the polyolefin surface, for example slip, can be improvedby blooming out. As mentioned, however, this phenomenon of migration andblooming out is unacceptable for the establishment of high-strengthbonds and/or coatings with foreign materials without any dependence ontime.

DETAILED DESCRIPTION OF THE INVENTION

The teaching of the invention as described in the following is based onthis knowledge of the relevant expert only briefly documented in theforegoing. The problem addressed by the present invention was to utilizethis technical effect of the migration of comparatively low molecularweight components after their incorporation in a high molecular weightpolyolefin-based polymer material and, by suitably modifying thisprocess, to secure the required objective of a permanent improvement inadhesion to polyolefin surfaces compared with bonds and coatingsinvolving standard auxiliaries, more particularly correspondingcatalyzed resins or catalyzed lacquers. More particularly, the problemaddressed by the invention was to establish high-strength bonds whichwould rule out unwanted adhesive failures and which would ensure thatthe adhesive joint could only be destroyed by cohesive failure or bycombined cohesive/adhesive failure.

In a first embodiment, therefore, the present invention relates topolyolefin-based moldings and films containing coupling internaladditives which are concentrated on the plastic surface throughmigration (blooming) and which, in their molecular structure, containcoupling substituents of high polarity on an oleophilic hydrocarbonresidue. These comparatively low molecular weight additives capable ofmigration are also referred to hereinafter as "additive (I)". The term"molding" is meant to be broadly interpreted and encompasses bothcorresponding rigid elements (for example sheets) and fibers and/orfilaments or workpieces produced using them.

The teaching according to the invention in this embodiment ischaracterized in that at least such a percentage of these internaladditives is fixed in the plastic surface and immobilized againstfurther migration by its hydrocarbon residues that permanently adhesivelayers and/or coatings can be applied to the polyolefin surface treatedin accordance with the invention without any need for additionalpretreatment thereof.

In another embodiment, the invention relates to a process for treatinghard polyolefin surfaces having substituents of high polarity and, ifdesired, chemical reactivity to corresponding reactive groups forimproving the adhesion of coating materials, more particularly lacquersand/or adhesives, to the polyolefin surface using coupling internaladditives in the polyolefin,

In this embodiment, the teaching according to the invention ischaracterized in that coupling internal additives (I) capable ofmigration, i.e. characterized by the blooming effect, are incorporatedin the polyolefin for processing and, after at least partial migrationto the surface, are immobilized there to such an extent that improvementof the adhesion of subsequently applied coatings and/or bonds isguaranteed largely independent of time. The notion of a guarantee withno dependence on time concerns both the time elapsing between productionof the particular polyolefin-based molding and its subsequent coatingwith lacquers or adhesives and the period of use of the multicomponentproduct produced by lacquering or coating with adhesives.

Finally, the invention relates to additive mixtures for solid plasticsbased on polyolefins, more particularly polyethylene and orpolypropylene, which--as an internal additive--improve coating withadhesives or lacquering behavior or generally adhesion to the polyolefinsurface. Corresponding particulars are given in the following.

The technical solution to the complex problem outlined above ofproviding a permanent and optimized improvement in the adhesion ofvirtually any materials to the surfaces of polyolefin-based plasticsessentially makes use of the known above-mentioned effect of separationby migration of comparatively low molecular weight constituents whichare intensively mixed with polyolefins, for example during theirprocessing by shaping. In this connection, the teaching according to theinvention seeks to influence the chemical character of these lowmolecular weight mixture components migrating outwards from the olefinbase in such a way that not only is migration as such guaranteed. Anessential step of the teaching according to the invention is to fixthese internal additives in the plastic surface through theirhydrocarbon residues and hence to immobilize them against furthermigration. The following technical result can thus be secured:functional groups of high polarity or even with reactivity to reactivecomponents from the coating compositions subsequently applied cancollect at the surface of the polyolefin molding in a predeterminedmanner in regard to type and concentration. These functional groups arean exposed constituent of the internal additive (I) which, with itshydrocarbon residue, remains in the molecular structure of thepolyolefin, again in a predetermined manner, and hence permanentlyunites the additive (I) with the polyolefin base.

The definition of the coupling internal additives (I) is of considerableimportance to the practical application of the working principleaccording to the invention. The following observations apply in thisregard. These additives, which are incorporated in the polyolefin-basedplastic in comparatively small quantities, are characterized by lowmolecular weights in comparison with the polymer components. An upperlimit to the molecular weight of suitable internal additives (I) is5,000 D (Dalton), preferably at most about 3,000 D and more preferablyat most about 1,000 D. Expression of the molecular weight in "Daltons"is known to be the definition (here the definition of the upper limit)as an absolute molecular weight. By comparison therefore with thepolyolefins with their molecular weights in the millions, comparativelylow molecular weight components are present here. Lower limits to themolecular weight of the internal additives (I) are about 70 to 100 D,preferably 150 to 180 D and more preferably about 200 to 300 D.

The chemical structure of the coupling internal additives (I) is anotherimportant factor. The following observations apply in this regard. Thechemical structure of the additives is generally a combination of asuitable hydrocarbon-based oleophilic basic molecule which has one ormore substituents of high polarity. Highly polar substituents such asthese are formed in known manner by molecular constituents containinghetero atoms, particular significance being attributed in this regard tothe hetero atoms O, N and/or halogen for forming the highly polarfunctional group(s).

In one particularly important embodiment of the teaching according tothe invention, the oleophilic hydrocarbon residue of the couplinginternal additives is additionally characterized in that at least partlyolefinically unsaturated elements are present therein. Preferredadditives (I) according to the invention are those which, in theirunreacted state, have iodine values of at least about 10, preferably ofat least about 30 to 40 and more preferably of at least about 45 to 50.As explained in detail hereinafter, both mono-olefinically unsaturatedhydrocarbon residues and polyolefinically unsaturated hydrocarbonresidues may be present in the additives (I) used in accordance with theinvention. Combinations of several corresponding compounds are alsoimportant auxiliaries for the purposes of the teaching according to theinvention. The particular iodine values of the additives (I) used mayassume values above 80 to 90 and, more particularly, values above 100.Highly unsaturated additive components with iodine values of up to about200 or even higher, for example in the range from 120 to 170, areauxiliaries in the context of the teaching according to the inventionwhich, on the one hand, can be immobilized particularly effectively inthe outer region of the solid polyolefin molding; on the other hand,these highly unsaturated additives are generally compounds which flow atroom temperature or at slightly elevated temperatures, for example attemperatures of up to 40 to 45° C. Where such components are used, themigration step crucial to application of the working principle accordingto the invention is facilitated just as much as immobilization of themigratable additive components in the outer regions of the polyolefinmolding.

So far as the three-dimensional structure of their hydrocarbon residueis concerned, the internal additives (I) may be both linear and branchedand/or may have a cyclic structure. The presence of adequateolefinically unsaturated elements also provides for the permanentincorporation of linear additives (I) in the polyolefin surface or outersurface. Heavily branched and/or cyclic structures of the hydrocarbonresidue can trigger an additional blockage of the migration effect,particularly in the uppermost layers of the polyolefin, so that theadditives in question are also physically immobilized in the outersurface of the polyolefin-based molding. Particulars of this will begiven in the following.

Basically, suitable substituents of high polarity are the manyfunctional groups which are distinguished in particular by a content ofhetero atoms and preferably by a content of O, N and/or halogen.Residues from the classes of carboxyl, hydroxyl, amino, oxazoline,epoxide and/or isocyanate groups and/or corresponding derivatives arementioned purely by way of example. Such derivatives include, forexample, ester groups, ether groups, amide groups/alkanolamine and/oralkanolamide groups.

Certain individually selected additives of the type in question andmixtures of several corresponding auxiliaries may be used as theadditive (I). The adhesive strength of the end product can be influencedin a predetermined manner by suitably selecting the couplingsubstituents of high polarity for the particular auxiliaries of thisclass that are added. However, mixtures of the type in question are alsocorresponding mixtures which, so far as their functional group isconcerned, may be assigned to a certain a sub-class, i.e. for examplecarboxyl groups as coupling substituents of high polarity, but whichhave different basic structures in their hydrocarbon molecule. It isknown that corresponding mixtures are obtained in particular wheremixtures of the type in question based on natural materials are used.For example, olefinically unsaturated fatty acid mixtures of vegetableand/or animal origin or derivatives thereof can be valuable additives ofthe type (I) for the purposes of the teaching according to theinvention.

As well known to the expert, different improvements in adhesion can beexpected in the subsequent coating step according to the particulargroups of high polarity. Relevant specialist knowledge is applicable inthis regard. However, particular significance is also attributed to thefollowing possible variation of the teaching according to the invention:

Coating compositions, such as lacquers or adhesives, can embody theprinciple of purely physical drying. However, they are often used asreactive compositions which lead to molecular enlargement and hence tocuring by reacting off in situ. Thus, in the adhesives field forexample, polyurethane-based multicomponent adhesives or epoxy adhesivesare known for their ability to form bonds of high strength. By suitablyselecting the functional groups of high polarity fixed at the polyolefinsurface in accordance with the invention, this component of theadditives (I) can additionally react off at least partly withcorresponding reactive components of the coating compositions oradhesives applied. This explains why carboxyl groups and/or hydroxylgroups can be particularly important as a constituent of the additives(I) according to the invention.

Another possibility for varying the composition of the additives (I)according to the invention lies in the number of functional substituentsof high polarity in the particular hydrocarbon skeleton. Even onesubstituent of high polarity can lead to the required permanent and, atthe same time, highly intensive increase in adhesion, particularly afteradaptation of the type and quantity of functional groups available. Inaddition, it has been found that the presence of several suchsubstituents of high polarity in the particular molecule of the additive(I) can be an important additional feature for increasing adhesivestrength. Reference is made purely by way of example here to the classof so-called dimer fatty acids which, through dimerization ofpolyethylenically unsaturated fatty acids by Diels-Alder condensation,form a hydrocarbon skeleton of complex and branched structure whichcombines sufficient olefinic double bonds for reactive fixing in thepolyolefin surface and, at the same time, two carboxyl groups permolecule unit. Dialkanol-amines containing at least partly olefinicallyunsaturated hydrocarbon residues or dialkanolamides of unsaturated fattyacids are highly effective adhesion promoters in the sense of theteaching according to the invention.

This applies in particular to the corresponding diethanol derivatives.This class includes, for example, oleic acid diethanolamide and linoleicacid diethanolamide. Expressly included in this connection arecommercial products known to the expert, including the secondarycomponents normally occurring therein. Examples of such commercialproducts are "Comperlan OD" (technical oleic acid diethanolamide) and"Comperlan F" (technical linoleic acid diethanolamide)--both knownproducts of Henkel KGaA. However, compounds belonging to the group ofsorbitan monoesters with, in particular, ethylenically unsaturated fattyacids also lead to optimal results in the context of the teachingaccording to the invention. The compounds specifically mentioned hereare merely examples of the structure of particularly effective internaladditives (I), on the basis of which a wide range of correspondinglyeffective additives can be selected with the aid of general specialistknowledge and used for the purposes of the teaching according to theinvention.

A first aspect of the teaching according to the invention is concernedwith the selection and determination of the coupling additives (I)according to molecule size and character of the various functional partsof the molecule. This determines the ability of the auxiliary uniformlyincorporated in the polyolefin to migrate after production of theparticular molding, for example by extrusion. The other complex ofdetermining elements described in the following is important to theapplication of the teaching according to the invention. This othercomplex of determining elements comprises immobilization of theadditives (I) concentrated in the surface of the plastic by chemicaland, preferably, catalytically induced and/or supported reaction ofreactive molecular constituents of the hydrocarbon residues of theadditives (I) with enlargement of the molecule and/or at least partialfixing of these additives by physical inhibition of any furthermigration. The variant of reactive immobilization of the initiallymigratable additive molecule is discussed first.

The ability to migrate in the molded polyolefin material is criticallyinfluenced by the size of the additive molecule. Depending on additionalphysical parameters, migration is increasingly impeded with increasingindividual (absolute) molecular weight so that, on reaching an adequatesize, the molecule is immobilized in the intended place even though,basically, it retains it tendency towards further migration. Theteaching according to the invention makes use of this. The couplingadditives (I) are used in admixture with the polyolefin solid initiallywith a molecule size which allows the predetermined migration into theouter regions of the polymer material. In the embodiment underdiscussion, however, a chemical reaction of the migrating additives inthis surface boundary zone is initiated or rather ensured by the use ofsuitable auxiliaries. The reason for this of course is that not only isatmospheric oxygen present at the outer surface of the plastic, theareas of plastic immediately adjacent the outer surface which arecrucial to the teaching according to the invention also take up certainquantities of atmospheric oxygen by diffusion. A sufficientlyolefinically unsaturated additive molecule can thus be oxidativelyreacted off in known manner with enlargement of the molecule. Suitablecoordination of the parameters to be taken into account here usinggeneral expert knowledge thus enables the object of the invention to beachieved, i.e. immobilizing initially migratable coupling additivemolecules in this outer zone of the plastic molding with enlargement ofthe molecule in such a way that sufficient and predeterminable numbersof functional groups of high polarity are available for the externalapplication of coating compositions and/or adhesives although theassociated hydrocarbon residues of these additive molecules still remainthoroughly mixed with the polyolefin molecule either directly orindirectly through other additive molecules. Accordingly, the oligo orpolymolecule of the coupling additive thus built up is able to performits designated function of permanently improving adhesion and, at thesame time, optimally increasing the improvement in adhesion.

The process sequence presented here as an example of the teachingaccording to the invention can be put into effect in various forms, someof which are described--again by way of example--in the following.

The internal coupling additives capable of reacting off, particularly inthe presence of oxygen, are incorporated in the polyolefin-based plastictogether with catalysts which promote reactive crosslinking at thesurface of the plastic. Accordingly, at least partly olefinicallyunsaturated additives (I) may be used together with catalysts, forexample based on transition metal salts. The catalytic curing ofolefinically unsaturated organic components of comparatively lowmolecular weight using such transition metal salts is known to theexpert, for example from the field of lacquers and coating compositions.The catalytically active transition metal salts are also known amongexperts as siccatives. Suitable siccatives are, for example, salts fromthe group consisting of Co, Zr, Fe, Pb, Mn, Ni, Cr, V and Ce. Evenextremely low concentrations of such transition metal salts, for examplein the lowermost ppm range or even far lower, show pronounced catalyticactivity in accelerating the curing of olefinically unsaturatedcomponents by oxidatively reacting off in the presence of atmosphericoxygen with enlargement of the molecule. Although the teaching accordingto the invention uses this knowledge as basically intended, the expertis also presented with the opportunity for optimization in eachparticular concrete case, thus securing the desired objective ofpermanence and optimization of the improvement in adhesion withoutcausing fundamental changes in the properties of the polyolefin-basedmaterial. The following additional considerations are relevant in thisregard:

Recent works by relevant experts are concerned with the problem ofmaking polymer materials based on polyolefins, more particularlypolyethylene and/or polypropylene, which are non-degradable or notreadily degradable by natural processes accessible to easier degradationunder environmental conditions by addition of selected additives. Thisis of interest, for example, for agricultural films, cf. in thisconnection PCT publication WO 93/12171. This document describes effortsto make thermoplastic polymer compounds of the type with which thepresent invention is also concerned degradable into a brittle materialunder composting conditions, i.e. a relative humidity of at least 80%and a temperature of 60° C., over a period of 14 days by incorporatingso-called auto-oxidative components together with predeterminedquantities of selected transition metals in the high molecular weightpolymer. According to the publication in question, suitableauto-oxidative components are, in particular, unsaturated fatty acidsand esters thereof which are said to be added in quantities of 0.1 to10% by weight, based on the mixture as a whole. At the same time, thesalts of selected transition metals, i.e. salts of cobalt, manganese,copper, cerium, vanadium and iron, are used as catalysts to initiate theoxidation in quantities of 5 to 500 ppm of the transition metal. The useof antioxidants is also proposed in order to stabilize thepolyolefin-based material during its period of use. Referring to therelevant prior art, the document in question states that these latestinvestigations have shown that the desired degradability of thepolyolefin material can only be achieved by using the right type andquantity of transition metal catalyst.

The teaching according to the invention differs from this prior art asfollows: the object of the teaching according to the invention is not toestablish or modify the potential degradability of polyolefin-basedmoldings and/or films. On the contrary, the invention seeks to leave thebasic polyolefin structure largely unchanged. Instead, the problemaddressed by the present invention was to improve adhesion to thesurfaces of polyolefin-based materials, i.e. to modify an importantparameter which is not discussed at all in the last prior-art documentcited above. The teaching according to the invention is based on theobservation that this problem can be solved by fixing the couplingadditive after it has migrated into the outer regions of the particularpolyolefin-based molding. Where auxiliaries as defined in the disclosureof PCT WO 93/12171 are used in the practical application of the teachingaccording to the invention, oxidative degradation of the polyolefin inthe context of the teaching of that document can be prevented fromoccurring in the multicomponent mixtures formulated in accordance withthe invention by limiting the quantity in which the siccative based onthe transition metals in question is used. In the Examples, it is shownthat the fixing of the coupling additives which have migrated into theouter regions, as desired in accordance with the invention, is initiatedwhere siccative contents well below 5 ppm are used. The siccativecontent can be reduced by several orders of magnitude below the lowerlimit of 5 ppm mentioned in the prior-art document in question withoutsignificantly limiting the desired improved in adhesion. In addition toand independently of this, the following observations apply in thisregard:

The siccatives based on transition metals defined in the foregoing forthe teaching according to the invention are more broadly defined thanthe specifically limited group of transition metals according to theteaching of the document under discussion. Moreover, the document inquestion states that only monocarboxylic acids and derivatives thereofare suitable as the auto-oxidative component whereas additives (I) whicheither contain several corresponding functional groups of high polarityon the molecule and/or which have a totally different structure orcharacter are particularly suitable for the teaching according to theinvention. However, the teaching according to the invention is notlimited in its application to the use of siccatives in the form of theoverlapping transition metal compounds. Working conditions and, inparticular, initiators or catalysts which are completely free fromtransition metals or transition metal compounds of the type underdiscussion may be used to fix the migratable coupling additives (I).

However, even in cases where siccatives of the type mentioned abovebased on transition metal compounds are used, the teaching according tothe invention--as explained--enables the improved adhesion required tobe achieved without at the same time endangering the properties of thebasic polymer material. One preferred embodiment is characterized by theuse of the siccatives in combination with additives (I) selected fromthe class of diethanolamides of unsaturated fatty acids. As alreadymentioned, the diethanolamides are preferably used in technical quality.Suitable siccatives for use in accordance with the invention are, forexample, organic compounds and, more particularly, correspondingcarboxylic acid salts of the particular transition metals. Thecarboxylic acids may additionally be selected so that, by virtue oftheir molecular structure, they themselves become the coupling internaladditive. However, taking into account the extremely small quantities ofsiccative required, this is merely a variant. Particularly usefulsiccatives can also be found in the class of relatively low saturatedfatty acids, for example containing 6 to 12 carbon atoms in the fattyacid molecule. These siccative fatty acids may even be linear.

Whereas, in the hitherto described specific embodiment of the teachingaccording to the invention, the optionally catalytically controlledautoxidation of the migratable additives (I) with enlargement of themolecule at the plastic surface is the crucial immobilization step, theteaching according to the invention affords other possibilities forapplying the stated principle. Thus, the hitherto specifically mentionedsiccatives may be replaced or accompanied by other catalyst systemswhich in turn migrate into the outer regions of the polyolefin-basedplastic molding where they initiate or secure the molecule-enlargingreaction of olefinically unsaturated internal additives (I) in thepresence of atmospheric oxygen and/or through the use of additionalauxiliaries. For example, the molecule-enlarging reaction can beinitiated in known manner by the input of energy in the form of suitablyselected high-energy radiation. Catalysts suitable for this purpose areknown from the prior art and are not dependent on the use of transitionmetals of the class of siccatives described above. In this way, theproblem addressed by the invention can be solved without having to useany metallic components.

In this connection, reference is made to another possible modificationof the teaching according to the invention. In addition to the olefinicdouble bonds mentioned above, other structural elements of the additivemolecule are basically suitable for a potential reaction of theadditives (I) at the plastic surface. Thus, it is known that branchedhydrocarbon residues can lead to structural units in the molecule whichare also catalytically suitable for reacting off with enlargement of themolecule. Tertiary carbon atoms in the molecule structure areparticularly appropriate in this regard. The modification of theteaching according to the invention under discussion here makes use ofthis well-known fact. In this case, too, an additive molecule which isnow aliphatically saturated, for example, is first exposed to migrationin the molded polyolefin material. Enlargement of the molecule thentakes place in the outer regions of the molding through reaction of theabove-mentioned functional elements of the additive molecule--againpreferably under the effect of correspondingly selected catalyticallyactive additives and/or additional energy supplied, for example, in theform of radiation. However, the teaching according to the inventiondiffers in this case, too, from the known finishing of the polyolefinsurface, for example by corona or plasma treatment. The workingprinciple according to the invention achieves the high adhesivestrengths required without having to resort to any such additionalpretreatment steps. However, combination of the working principleaccording to the invention with known measures for increasing adhesionis not of course out of the question and falls within the scope of theteaching according to the invention.

In one important embodiment of the teaching according to the invention,the migratable coupling additives (I) are used together with anotheradditive component which is referred to hereinafter as "additive (II)".This class of additives comprises relatively high molecular weightcompounds containing olefinically unsaturated groups which arecorrespondingly limited in their mobility in the polyolefin-basedplastic. Preferred additives (II) are corresponding oligomer or polymercomponents with molecular weights of up to about 1 million D, the lowerlimit to the molecular weight being freely selectable providingmigration is adequately inhibited in the final polyolefin molding.Suitable lower limits for the molecular weight of the additives (II)are, for example, 10,000 D or lower, preferably 50,000 to 75,000 D orlower and more preferably at least 100,000 D. In this case, too, thepotential mobility of the additive (II) in the solidified polyolefinmolding can be additionally influenced through structural parameters,for example through a complex three-dimensional structure of theadditive (II).

The additives (II) are preferably distributed at least substantiallyuniformly in the polyolefin polymer in the same way as the otheradditives hitherto described. However, the additive (II) largely retainsits spatial distribution and association in the following migrationstep. In its/their subsequent fixing, the additive component(s) (I) cannow be linked to the additive component(s) (II). It is clear that thiscan have a positive effect on the fixing of the coupling additivecomponent(s) (I) desired in accordance with the invention.

In principle, the additive (II) may be selected from oligomer or polymercomponents of adequate molecular weight providing their molecularstructure contains reactive ethylenic double bonds for potential linkingof the additive component(s) (I). Unsaturated alkyd resins preferablywith an oil length of 20 to 70% are mentioned purely by way of example.Other examples include butadiene derivatives, isoprene derivatives,allyl-containing polymers, unsaturated polyesters based on polybasiccarboxylic acids and/or poly-(meth)acrylates containing residues ofunsaturated fatty alcohols.

Where the additives (I) and (II) are used together, they may be employedin quantity ratios (additive (I) : additive (II)) of 10:1 to 1:3 andpreferably in quantity ratios of 8:1 to 1:1. In the importantembodiments, therefore, additive (II) is generally used in a smallerquantity than or at most in the same quantity as additive (I). Theadditive mixtures are added to the polyolefin-based plastic inquantities of generally 0.01 to 10% by weight and preferably 0.1 to atmost about 5% by weight and, more particularly, in quantities of atleast 0.5 to 1 or 3% by weight, based on polyolefin-based plastic.

Taking into account the above-described embodiment in which siccativesare used as an additional catalytic aid for immobilizing the migratableadditives (I), preferred mixtures of the additive types in question andthe siccative are those which contain the individual components in thefollowing quantities (% by weight, based on the additive mixture):

additive I: 5 to 100% by weight, preferably 25 to 99% by weight

additive II: 0 to 80% by weight, preferably 9 to 50% by weight

siccative: 0 to 20% by weight, preferably 0 to 12% by weight.

As can be seen from these figures, the additives (I) are generally usedin the largest quantities. The non-migratable or substantiallynon-migratable additives (II) optionally used as auxiliaries areuniformly distributed in the polyolefin-based plastic during theirincorporation. Accordingly, they are also present in the regions nearthe surface important for the immobilization of the migratable additivecomponents (I). By virtue of their olefinically unsaturated elements,they are capable of reacting off with the additives (I). Preferrediodine values for the additives (II) according to the invention are inthe range from about 50 to 150 and, more particularly, in the range fromabout 70 to 130.

The siccatives and/or other catalysts or initiators used in thepreferred embodiments to fix and immobilize the additives (I) may beused in the comparatively very small quantities which correspond toexpert knowledge on the catalytic induction of such reactions. Asalready mentioned, it has been found that the use of, for example,siccatives based on transition metals in concentrations well below theppm range leads to effective immobilization of the additives (I) in theintended region, i.e. the uppermost layers of the solid plasticmaterial.

The following observations relates to the character of the additives (I)or additive mixtures to be used in each individual case. The migrationrate of these materials is very largely determined by their molecularstructure. Linear or only lightly branched hydrocarbon residues, forexample of the preferred range from about C₁₂ to C₃₆ and, moreparticularly, from about C₁₂ to C₂₄, migrate comparatively quickly sothat optimum adhesion values are developed in a comparatively shorttime. For example, maximum adhesion levels can be determined after onlyabout 1 to 3 days.

If, by contrast, additives or additive mixtures (I) of comparativelymore complex and/or larger molecular structure, for example with up to45 or 50 carbon atoms in the individual molecule, are used, the verymuch slower migration of such coupling additives is reflected in thefact that the potential adhesion levels to be determined rise over aconsiderable period of, for example, 2 to 3 weeks and only remainsubstantially constant thereafter. In their case, the coupling groups ofhigh polarity evidently collect comparatively slowly on the outersurface of the polyolefin moldings and, in the subsequent coating step,are able to interact with the lacquer and/or the adhesive. Acharacteristic example of such a comparatively slowly migrating additive(I) are the balsam resins (Indonesian tree resin) based largely onabietic acid. Relevant numerical data can be found in the followingExamples. The migration rate to be expected from the molecular structureof the particular additives (I) used can also be one of the determiningfactors for the particular quantity of additives (I) to be used in eachindividual case. Lower limits to the amount of additive (I) incorporatedin the polyolefin are about 0.01% by weight and, more particularly,about 0.1% by weight. In general, it will be appropriate to use at leastabout 0.2 to 0.8% by weight, based on the weight of the oleophilicpolyolefin. Optimal adhesion values for the representatives of additiveclass (I) used in each individual case are generally achieved withadditions of about 1 to 5% by weight and, more particularly, up to about3% by weight. However, it may even be appropriate to use the additivecomponents (I) in even larger quantities, for example in quantities ofup to about 10% by weight.

As already mentioned, the optimal adhesive strength to be established isunderstandably determined by the chemical nature and the possibleinteraction of the substituents of high polarity and, optionally,reactivity in the additive (I). The choice of the additives (I) to beused in each individual case is determined inter alia by the particularstresses likely to be applied to the bond between the polyolefin and theforeign material applied in the end product. In general, adhesion values(determined as tensile shear strength by the standard method describedin the Examples) of at least about 1 N/mm² and preferably of at least1.2 N/mm² can be achieved in accordance with the invention. In addition,it can be of advantage to establish adhesion values of at least 1.5 to1.8 N/mm², adhesive strengths of at least 2.0 N/mm² being preferred forheavily stressed composite materials. According to the invention,adhesive strengths of this order can always be achieved by suitablyselecting the coupling additives.

The numerical data in the Examples show that the immobilization of theadditive component (I) in accordance with the invention is cruciallyimportant to the durability of the bonding effect. Although saturatedcarboxylic acids, for example of the stearic acid type or the even moreeffective corresponding linear carboxylic acids with slightly shorterhydrocarbon chains in the molecule, can lead to good adhesion levels inthe short term, the strength of adhesion obtainable decreasescontinuously in the event of storage of correspondingly finishedpolyolefin solids. The situation is totally different with the couplingadditives (I) immobilized in the boundary surface region in accordancewith the invention. In their case, optimal adhesion levels onceestablished are maintained for long periods or even increase in theevent of prolonged storage.

The combination of adhesion levels increased in accordance with theinvention with known technologies for improving strength of adhesion topolyolefin surfaces falls within the scope of the teaching according tothe invention. Thus, both mechanical and chemical and/or physicalsurface treatments of the outer polyolefin surface can be combined withthe modifications to adhesive strength achieved in accordance with theinvention. However, this is generally not necessary.

The internal coupling additives and the siccatives or initiatorsoptionally used may be incorporated in the polyolefin-based oleophilicsolid material by methods known per se. Thus, it will generally beappropriate to pre-blend the additives with limited quantities of thepolyolefin to form mixtures of relatively high concentration which canbe presented, for example, as granules. The granules thus formed aresubsequently incorporated in the polyolefins or polyolefin mixturesduring their shape-creating processing, uniform incorporation beingappropriate. Any initiators, siccatives and the like used may becorrespondingly pre-blended in a separate step and added to the endproducts in the final mixing step.

The oleophilic polyolefin material may be selected from any of thenumerous known polymer and copolymer types based on polyethylene orpolypropylene, as described for example in the prior-art literaturecited at the beginning. Mixtures of pure polyolefins with copolymers arealso suitable in principle providing the migratability of the additives(I) according to the invention remains intact and their accumulation inthe solid surfaces is thus guaranteed. Polymer types particularlysuitable for the teaching according to the invention are listed below:

Poly(ethylenes) such as HDPE (high-density polyethylene), LDPE(low-density polyethylene), LLDPE (linear low-density polyethylene),MDPE (medium-density polyethylene), UHMPE (ultra high molecularpolyethylene), VPE (crosslinked polyethylene), HPPE (high-pressurepolyethylene); poly(styrene); poly(methylstyrene); poly(oxymethylene);metallocene catalyzed cycloolefin copolymers, such asnorbornene/ethylene copolymers; copolymers containing at least 80% ofethylene and/or styrene and less than 20% of monomers, such as vinylacetate, acrylates, methacrylates, acrylic acid, acrylonitrile, vinylchloride. Examples of such polymers are poly(ethylene-co-ethylacrylate), poly(ethylene-co-vinyl acetate), poly(ethylene-co-vinylchloride), poly(styrene-co-acrylonitrile). Also suitable are graftcopolymers and polymer blends, i.e. mixtures of polymers containinginter alia the polymers mentioned above, for example polyethylene-basedpolymer blends.

EXAMPLES

In the following Examples set out in tabular form,

material samples produced under standardized conditions

are subjected to standardized coating (with adhesives or lacquers) andthe test materials thus produced

are evaluated in standardized tests.

(A) Materials Used

In all the tests, the high molecular weight polyolefin used is acorresponding polyethylene of the LDPE type ("Lupolen H 1800", a productof BASF).

In the Tables, the auxiliaries used in each particular Example(relatively low molecular weight additive components (I), relativelyhigh molecular weight additive components (II) and/or siccatives andoptionally other additives--are assigned to each individual Example interms of type and quantity and identified.

In each particular Example, additives of limited molecular weight, moreparticularly additives (I) according to the invention, are characterizedeither by their commercial names or by chemical identification. Wheretrade names (for example "Edenor SbO5") are used in the Tables,particulars of the chemical character of the additives in question canbe found in the "Appendix to the Examples" which follows the Tables.

The relatively high molecular weight additives (II) are alsocharacterized in the Tables by their commercial names (for example"Alkydal F681") or by reference to the resin types for "test 1" and"test 2" described in detail in the Appendix. All the particularsrequired for chemical identification can be found in the above-mentioned"Appendix to the Examples".

In the Examples, a mixture--described as "siccative" --of a cobalt,zirconium and lead octoate in toluene with a metal content of 1.04% byweight Co, 2.48% by weight Zr and 9.93% by weight Pb is used in almostevery case as the catalytically active component for fixing themigratable additives (I).

Where other hardener components are used in individual Examples, theyare identified in detail.

The polyurethane-based and epoxy-based reactive adhesives (Makroplast,Stabilit Ultra) used for bonding are identified by these commercialnames in the Tables. A more detailed definition can again be found inthe "Appendix to the Examples".

The same applies to the lacquers (lacquer I and lacquer II) used in thelacquering tests, of which the composition is again listed in the"Appendix to the Examples".

(B) Preparation of the Material Samples to be Tested

This is carried out as follows:

The mixtures listed in the Examples are produced by compounding in aBrabender Plasticorder PL 2000 twin-screw extruder with a screw diameterof 41.8 mm and a screw length of 7 D. The following temperatures areestablished in the heating zones: heating zone I 220° C., heating zoneII 230° C., heating zone IlI 240° C. and slot die 250° C. The dimensionsof the extrusion die are 50×0.5 mm so that a strip approximately 45 mmwide and 0.5 mm thick is formed. These strips were used for all thetests.

Bonding under standardized conditions is carried out as follows:

The two-component adhesives are stirred in non-reusable aluminium dishesand directly processed. The extruded PE strips are coated with adhesiveover an area of 25×25 mm=625 mm² between two wooden spatulas so that twobonded areas are obtained between the spatulas and the PE strips. Thewooden spatulas used have the following dimensions: length 10 cm, width2.5 cm, thickness 0.2 cm.

Lacquering with the lacquers identified in the Examples is also carriedout in known manner on the above-described PE strips.

(C) Testing of the Bonded or Lacquered Material Samples

This is carried out by the following generally accepted tests:

Determination of adhesive strength by tensile shear testing (DIN 53263)under the following standard conditions:

Tensile shear test: the tensile shear tests are carried out with a ZwickUniversal testing machine. The test speed is 15 mm/minute. The valuesshown in the Tables where they are assigned to the particular mixturesrepresent averages of 5 individual measurements. The force measured onfailure is determined (in N/mm²).

To test lacquer adhesion, a lattice of 5×5=25 squares with an edgelength of 1×1 mm is cut with a knife into the air-dried lacquer film ofthe particular material sample. A piece of Tesa film is then applied tothe lattice, pressed on firmly with a finger nail and then suddenlypeeled off.

The result is expressed as the number of square paint segments out ofthe 25 still adhering to the polyolefin surface. The larger this number,the better the adhesion of the lacquer layer to the polyethylenesurface.

In addition to the auxiliaries incorporated ("mixture") and thequantities in which they are used (g), the number of days elapsingbetween extrusion of the polyethylene-based strip and bonding understandardized conditions is also shown in the following Tables. Anyextraction treatment of the extruded strip additionally applied overthis period is described in the particular individual case. The lastcolumn of the Example shows the adhesion values obtained in theabove-described standard test where bonding is carried out with thepolyurethane-based adhesive "Makroplast".

In a first series of tests, blank adhesion values are determined underthe described standard conditions, the respective measurements beingbased on the polyethylene-based material samples identified in thefollowing Table.

Blank Values:

    ______________________________________                                                                   Makroplast                                         Material        Adhesive   Fmax (N/mm.sup.2)                                  ______________________________________                                        Polyethylene    Makroplast 0.27                                               (Lupolen H 1800)                                                                              (PU adhesive)                                                 Polyethylene    Makroplast 3.48                                               (corona-treated)                                                                              (PU adhesive)                                                 Polyethylene    Makroplast 2.35                                               (Lupolen H 1800)                                                                              (PU adhesive)                                                 pickled with chromosulfuric acid                                              Wood/wood       Makroplast 3.96                                                               (PU adhesive)                                                                            (pure cohesive failure)                            ______________________________________                                    

                  TABLE                                                           ______________________________________                                                                             Makroplast                                                Quantity Bonded × days                                                                      Fmax                                     No.  Mixture     (g)      after extrusion                                                                          (N/mm.sup.2)                             ______________________________________                                        1    Edenor SbO5 9        1          3.32                                          Siccative   0.19                                                         2    Edenor SbO5 9.0      1          3.23                                          Siccative   0.38     7 (including 1 day's                                                                     2.74                                                               extraction with                                                                          3.34                                                               CH.sub.2 Cl.sub.2)                                                                       2.88                                                               31 (including 1                                                               day's extraction                                                              with CH.sub.2 Cl.sub.2)                                                       31 (including 3                                                               days' extraction                                                              with CH.sub.2 Cl.sub.2)                             3    Edenor FTi  9.0      1          2.46                                          Siccative   0.38     16         3.75                                     4    Edenor UKD  9.0      1          2.79                                          6010                                                                          Siccative   0.5                                                          5    Indonesian tree                                                                           9.0      1          1.06                                          resin       0.27     14         1.45                                          Siccative            55         2.55                                     6    Indonesian tree                                                                           6.3      2          1.13                                          resin       2.7      50         2.10                                          Edenor SbO5 0.19     63         2.09                                          Siccative                                                                7    Indonesian tree                                                                           3.6      5          1.25                                          resin       5.0      11         1.44                                          Edenor SbO5 0.11     52         2.07                                          Siccative                                                                8    Indonesian tree                                                                           2.7      6          1.53                                          resin       6.3      48         2.02                                          Edenor SbO5 0.08                                                              Siccative                                                                9    Dimer fatty acid                                                                          9.0      3          2.69                                          Siccative   0.38                                                         ______________________________________                                    

Examples 1 to 4 use relatively quickly migrating additives (I) accordingto the invention with different contents of ethylenically unsaturatedcomponents (see Appendix). Examples 5 to 8 use the relatively slowlymigrating indonesian tree resin based on abietic acid as additive (I) oras part of a mixture with the comparatively more quickly migratingadditive based on the unsaturated fatty acid. In Example 9, C₃₆ dimerfatty acid (iodine value 136), which is characterized by two polarsubstituents on the oleophilic hydrocarbon molecule, is used as additive(I). Despite the comparatively large hydrocarbon molecule, a high bondstrength value is measured.

Examples 10 to 16 below are intended to illustrate the characteristicelement of the teaching according to the invention that even extremelysmall traces of the siccative lead to extremely effective immobilizationof the additive (I).

    ______________________________________                                                        Quantity  Bonded × days                                                                    Makroplast                                 No.  Mixture    (g)       after extrusion                                                                        Fmax (N/mm.sup.2)                          ______________________________________                                        10   Edenor SbO5                                                                              9.0       1        2.62                                            Siccative  0.25                                                          11   Edenor SbO5                                                                              9.0       1        2.56                                            Siccative  0.1                                                           12   Edenor SbO5                                                                              9.0       1        2.63                                            Siccative  0.01                                                          13   Edenor SbO5                                                                              9.0       1        2.45                                            Siccative  0.005                                                         14   Edenor SbO5                                                                              9.0       1        3.06                                            Siccative  0.001                                                         15   Edenor SbO5                                                                              9.0       1        2.33                                            Siccative  0.0005                                                        16   Edenor SbO5                                                                              9.0       1        2.86                                            Siccative  0.0002                                                        ______________________________________                                    

Examples 17 to 24 below use mixtures of additives (I) with additives(II) as the additives according to the invention. On the one hand, themixing ratios are varied; on the other hand, the particular types ofadditive (II) are varied. With regard to additive (I), a rapidlymigrating type (Edenor SbO5) is compared with a comparatively slowlymigrating type (Indonesian tree resin).

    ______________________________________                                                        Quantity  Bonded × days                                                                     Makroplast                                No.  Mixture    (g)       after extrusion                                                                         Fmax (N/mm.sup.2)                         ______________________________________                                        17   Alkydal F681                                                                             12.6      2         2.10                                           (50%)      2.7       12        2.03                                           Edenor SbO5                                                                              0.19      13        2.36                                           Siccative            28        2.09                                                                35        2.20                                      18   Alkydal F681                                                                             6.7       2         1.97                                           (50%)      2.7       35        2.23                                           Edenor SbO5                                                                              0.1                                                                Siccative                                                                19   Alkydal F681                                                                             7.2       35        2.36                                           (50%)      5.4                                                                Edenor SbO5                                                                              0.11                                                               Siccative                                                                20   Alkydal F681                                                                             3.6       4         2.63                                           (75%)      6.3                                                                Edenor SbO5                                                                              0.19                                                               Siccative                                                                21   Alkydal F681                                                                             9.0       7         0.73                                           (50%)      4.5                                                                Indonesian tree                                                                          0.14                                                               resin                                                                         Siccative                                                                22   Alkydal F681                                                                             6.3       1         0.85                                           (50%)      5.4                                                                Indonesian tree                                                                          0.08                                                               resin                                                                    23   Resin test 1                                                                             2.7       1         2.91                                           Edenor SbO5                                                                              6.3       11 (including 3                                                                         2.92                                           Siccative  0.19      days' extraction                                                              in CH.sub.2 Cl.sub.2)                               24   Resin test 1                                                                             6.3       4         0.51                                           Edenor SbO5                                                                              2.7                                                                Siccative  0.19                                                          25   Alkydal R35                                                                              8.25      1         0.98                                           Edenor SbO5                                                                              4.1                                                                Siccative  0.15                                                               Dhydril NRC                                                                              0.03                                                          26   Alkydal R35                                                                              6.0       1         1.55                                           Edenor SbO5                                                                              5.4                                                                Siccative  0.108                                                              Dehydril NRC                                                                             0.02                                                          ______________________________________                                    

In Examples 27 and 28, the migratable additive (I) is omitted from thepolyethylene and only migration-inhibited additives (II) are added. Theadhesion values determined are almost identical with the blank valueshown above for pure polyethylene.

    ______________________________________                                                        Quantity  Bonded × days                                                                    Makroplast                                 No.  Mixture    (g)       after extrusion                                                                        Fmax (N/mm.sup.2)                          ______________________________________                                        27   Alkydal F681                                                                             9.5       2        0.23                                            (50%)      0.29      36       0.32                                            Siccative                                                                28   Alkydal R35                                                                              15.0      7        0.31                                            Siccative  0.27                                                          ______________________________________                                    

Examples 29 to 36 below modify the amount of additive (rapidly migratingand comparatively highly unsaturated additive (I)) added to apredetermined mixture and illustrate the dependence of the adhesionvalues obtainable. A significant reduction in the adhesion values onlyoccurs at very low concentrations of the additive (I) in thepolyethylene.

    ______________________________________                                                        Quantity Bonded × days                                                                      Makroplast                                No.  Mixture    (g)      after extrusion                                                                          Fmax (N/mm.sup.2)                         ______________________________________                                        29   Edenor SbO5                                                                              30.0     1          2.80                                           Siccative  0.38     10         2.86                                      30   Edenor SbO5                                                                              15.0     1          2.44                                           Siccative  0.38     10         2.92                                                               15 (2 days at                                                                            2.43                                                               55° C.)                                       31   Edenor SbO5                                                                              6.0      1          2.66                                           Siccative  0.38     10         3.17                                      32   Edenor SbO5                                                                              3.0      1          2.19                                           Siccative  0.38     10         2.16                                      33   Edenor SbO5                                                                              1.2      1          1.75                                           Siccative  0.38     10         2.84                                      34   Edenor SbO5                                                                              0.5      1          1.77                                           Siccative  0.38                                                          35   Edenor SbO5                                                                              0.1      1          1.18                                           Siccative  0.38                                                          36   Edenor SbO5                                                                              0.01     1          0.67                                           Siccative  0.38                                                          ______________________________________                                    

Examples 37 to 43 below relate to the determination of adhesion valuesin the absence of the siccative using--on the one hand--rapidly or evenrelatively slowly migrating additives (I), which can be permanentlyfixed in the surface of the polyethylene material in the context of thedefinition according to the invention, and--on the other hand (forcomparison)--saturated carboxylic acids of the stearic acid, isostearicacid and capric acid type as additives. In this case, the additivecannot of course be fixed by oxidation.

The Table shows the adhesive strength values as a function of the timelapsing between production of the polyethylene-based strip and itsbonding under the standardized conditions defined above.

    ______________________________________                                                        Quantity Bonded × days                                                                      Makroplast                                No.  Mixture    (g)      after extrusion                                                                          Fmax (N/mm.sup.2)                         ______________________________________                                        37   Edenor SbO5                                                                              9.0      1          1.82                                                               6          2.21                                                               21         2.78                                                               25 (3 days' extrac-                                                                      2.73                                                               tion in CH.sub.2 Cl.sub.2)                                                    26         2.96                                                               40         2.68                                      38   Indonesian tree                                                                          9.0      8          0.33                                           resin               11         0.40                                                               67         0.56                                      39   Dimer fatty                                                                              9.45     3          2.68                                           acid                                                                     40   Stearic acid                                                                             9.0      1          1.26                                                               2          0.90                                                               7          0.86                                                               20         0.63                                      41   Isostearic acid                                                                          6.0      1          1.82                                                               7          1.22                                                               19         1.19                                      42   Isostearic acid                                                                          15.0     1          2.44                                                               7          2.13                                                               7 (2 days at 55° C.)                                                              1.89                                                               19         1.93                                      43   Capric acid                                                                              9.0      1          2.28                                           (C10)               3          1.83                                                               7          1.59                                                               21         1.40                                      ______________________________________                                    

The considerable loss of adhesion with increasing time interval betweenproduction of the plastic strip and its bonding under standardconditions where the saturated fatty acids are used as additive (I) isstriking.

Comparable results are obtained where fully saturated, rapidly migratingadditives of the capric acid and isostearic acid type are added, even inthe presence of the siccative, see Examples 44 to 49 below.

    ______________________________________                                                        Quantity  Bonded × days                                                                    Makroplast                                 No.  Mixture    (g)       after extrusion                                                                        Fmax (N/mm.sup.2)                          ______________________________________                                        44   Capric acid                                                                              9.0        3       1.75                                            Siccative  0.38      15       0.99                                       45   Isostearic acid                                                                          1.2        1       1.12                                            Siccative  0.38       7       0.92                                                                 19       0.72                                       46   Isostearic acid                                                                          3.0        1       1.46                                            Siccative  0.38       7       1.06                                                                 19       0.83                                       47   Isostearic acid                                                                          6.0        1       1.95                                            Siccative  0.38       7       1.30                                                                 19       0.99                                       48   Isostearic acid                                                                          9.0        1       2.36                                            Siccative  0.38      15       1.42                                       49   Isostearic acid                                                                          15.0       1       2.28                                            Siccative  0.38       7       1.68                                                                 19       1.62                                       ______________________________________                                    

Further variations of the teaching according to the invention are givenin Examples 50 to 52 below. In Example 50, a carboxylic acid methylester group is used as the coupling functional group. Although theadhesion values obtainable are lower by comparison with the carboxylgroup, they are still far higher than the blank value.

Examples 51 and 52 use a cobalt salt (cf. "test 3" below) and iron saltof an ether carboxylic acid instead of the "siccative" defined above.

    ______________________________________                                                         Quantity Bonded × days                                                                     Makroplast                                No.  Mixture     (g)      after extrusion                                                                         Fmax (N/mm.sup.2)                         ______________________________________                                        50   Edenor MeTiO5                                                                             9.0      1         0.53                                           Siccative   0.38     10        0.93                                      51   Ether carboxylic                                                                          1.8      5         2.42                                           acid, Co salt        25 (incl. 3 days'                                                                       1.95                                           from test 3          extraction with                                                                         2.00                                                                CH.sub.2 Cl.sub.2)                                  52   Ether carboxylic                                                                          1.8      1         1.87                                           acid, Fe salt                                                                 from test 3                                                              ______________________________________                                    

The following Table covering examples 53 to 63 shows the result of acomparison of various functional groups in the additive (I) for adhesionto polythylene. The adhesives used for bonding are an epoxy adhesive(Stabilit Ultra) and the previously used polyurethane adhesive(Makroplast).

    __________________________________________________________________________    Comparison of various functional groups for adhesion to PE                                           Epoxy adhesive   PU adhesive                                           Epoxy adhesive                                                                       (Stabilit Ultra)                                                                         PU adhesive                                                                         (Makroplast)                                          (Stabilit Ultra)                                                                     +0.38 g siccative/600 g                                                                  (Makroplast)                                                                        +0.38 g siccative/600 g                  9 g of Substance to 600 g of                                                               No siccative                                                                         polyethylene                                                                             No siccative                                                                        polyethylene                          No.                                                                              polyethylene (N/mm.sup.2)                                                                         (N/mm.sup.2)                                                                             (N/mm.sup.2)                                                                        (N/mm.sup.2)                          __________________________________________________________________________    53 Soya alkyl oxazoline                                                                       0.85   1.04       0.54  2.26                                  54 Stearic acid amide                                                                         0.74   0.56       0.91  0.71                                  55 Erucic acid amide                                                                          --     1.05       0.31  1.53                                  56 Oleic acid amide                                                                           0.68   1.76       0.26  1.69                                  57 HD Ocenol 150/170                                                                          1.38   1.49       0.40  1.31                                  58 Glycerol monooleate                                                                        0.63   2.01       0.31  1.53                                  59 Sorbitan monooleate                                                                        0.63   3.54       0.32  2.72                                  60 Edenor SbO5  --     1.35       1.82  3.3                                   61 Edenor MeTiO5                                                                              --     --         0.2   0.53                                  62 C.sub.16 Alkenyl-SM                                                                        --     --         0.35  0.37                                  63 Oleic acid diethanolamide                                                                  3.32   2.52       2.41  2.26                                  __________________________________________________________________________

Lacquer Adhesion Tests

The adhesion of lacquer layers to the surface of untreated polyethylene,siccative-containing polyethylene and polyethylene mixtures modified inaccordance with the invention is investigated in a series of furthertests. The procedure adopted is the same as described in detail at thebeginning of the Examples under section (C) (cross-hatching with 25 1×1mm squares).

Lacquers I (polyurethane-based) and II (acrylicresin/polyurethane-based) are used. Further particulars of theselacquers can be found in the Appendix to the Examples.

The particular materials used and the lacquering results obtained areset out in the following Table. In every case, the lacquer was appliedabout 1 week after preparation of the particular polyethylene-basedmulticomponent mixture. Regular measurement of the adhesion of materialsselected at random does not show any deterioration in the paint adhesionvalues, even after storage for 6 weeks at 60° C.

    ______________________________________                                                           Lacquer I    Lacquer II                                                       Squares remaining                                                                          Squares remaining                                      Quantity in                                                                             mm.sup.2 (multiple                                                                         mm.sup.2 (multiple                            Mixture  600 g PE (g)                                                                            measurement) measurement)                                  ______________________________________                                        Pure poly-                                                                             0.19      0 0          0 0                                           ethylene                                                                      (Lupolen                                                                      H1800)                                                                        Siccative                                                                              0.19      0 0 0        0                                             Edenor SbO5                                                                            9.0       25 25        25 25                                         Edenor SbO5                                                                            9.0       23 2 22      25 25                                         Siccative                                                                              0.19                                                                 Edenor SbO5                                                                            9.0       25 25 24     25 25 25                                      Siccative                                                                              0.38                                                                 Edenor SbO5                                                                            9.0       25 25 25     25 25                                         Siccative                                                                              1.0                                                                  Edenor SbO5                                                                            1.2       n.d.         25 24 25                                      Siccative                                                                              0.38                                                                 Edenor SbO5                                                                            9.0       n.d.         25 25 25                                      Siccative                                                                              0.005                                                                Indonesion tree                                                                        9.0       n.d.         25 25 25                                      resin                                                                         Siccative                                                                              0.27                                                                 Indonesian tree                                                                        5.9       25 25 25     25 25                                         resin                                                                         Edenor SbO5                                                                            3.6                                                                  Siccative                                                                              0.19                                                                 Alkydal F681                                                                           12.6      n.d.         25 25                                         (50%)                                                                         Edenor SbO5                                                                            2.7                                                                  Siccative                                                                              0.19                                                                 ______________________________________                                    

Identification of Chemicals

As mentioned at the beginning of the Examples, further particulars ofthe chemical characteristics of individual additives (I), additives(II), adhesives and lacquers I and II used in the Examples are set outin the following Appendix.

    ______________________________________                                        Individual chemicals:                                                         ______________________________________                                        Dehydril NRC: anti-skinning agent (a product of Henkel                                      KGaA)                                                           Oleic acid diethanolamide:                                                                  commerical product ("Comperian OD", a                                         product of Henkel KGaA), used in Example                                      63                                                              HD-Ocenol 150/170:                                                                          unsaturated fatty alcohol with an iodine                                      value of 150 to 170 (a product of Henkel                                      KGaA).                                                          Additive (I):                                                                 Edenor SbO5:  polyunsaturated C.sub.18 fatty acid with an iodine                            value of 135 to 145                                             Edenor UKD 6010:                                                                            highly unsaturated C.sub.18 fatty acid with an                                iodine value of 140-148 (content of C.sub.18                                  "conjugated fatty acids 58 to 62% by weight)                    Edenor FTi:   C.sub.14-18 fatty acids with an iodine value of 48                            to 54 (C.sub.18 ' 40% by weight)                                Edenor TiO5:  predominantly unsaturated C.sub.16/18 fatty acid                              with an iodine value of 89 to 97                                Edenor MeTiO5:                                                                              methyl ester of predominantly unsaturated                                     C.sub.16/18 fatty acids with iodine values of 89 to                           97                                                              ______________________________________                                    

All the Edenor fatty acid types mentioned here are commercial productsof Henkel KGaA which are described in the relevant scientific literatureunder the protected trade names mentioned.

    ______________________________________                                        Additive (II):                                                                ______________________________________                                        Alkydal F681:                                                                             a product of Bayer AG, long-oil alkyd resin                                   which is used, for example, as an artist's paint                              and which contains 66% of drying vegetable                                    fatty acids, acid value >20                                       Alkydal R35:                                                                              a product of Bayer AG, a universal resin for                                  industrial primers and finishing lacquers                                     based on a short-oil alkyd resin with a content                               of about 32% castor oil, acid value 18 to 25                      ______________________________________                                    

Additive (II) for "Test 1"

A mixture of 334 g of methyl acrylate, 208 g of styrene and 8.1 g ofdicumyl peroxide is slowly added dropwise (7 h) to 650 g of hexanol at areaction temperature of 135° C. 650 g of HD Ocenol 150/170 are thenadded. The hexanol is distilled off. 3.4 g of an organotin catalyst("Swedcat 5" a product of Swedstab) are then added at 180° C. Methanolseparates at 180° C. The reaction is terminated when methanol stopsseparating. A resin highly viscous at room temperature is obtained.Yield 1129.6 g, OH value 7.7, acid value 0.5, saponification value 156,iodine value 94.

Additive (II) for "Test 2":

29.1 g of diethylene glycol, 22.4 g of maleic anhydride and 0.1 g ofp-toluene sulfonic anhydride are introduced into a reaction vessel andstirred. The reaction vessel is then evacuated and purged with nitrogenthree times. The reaction mixture is heated to 140° C. and, after areaction time of 1 h, the temperature is increased to 160° C. and wateris removed until the acid value is <8. The polyester obtained has a meltviscosity of 120 to 160 mPas (100° C., 2500 s⁻¹) and an iodine value of136.

The Reactive Adhesives Used for Bonding:

Makroplast, polyurethane adhesive (a product of Henkel KGaA) consistingof the resin component known commercially as UK 8109 and the hardenercomponent UK 5430 in a ratio of 5:1. The hardener containsdiphenylmethane-4,4'-diisocyanate; pot life about 1 hour.

Stabilit Ultra, epoxy adhesive (a product of Henkel KGaA) consisting ofepoxy resin (Metallon E2108) and diamine hardener in a ratio of 10:6,pot life about 30 minutes.

The Lacquers Used for Surface Lacquering:

Lacquer I (polyurethane lacquer):

2.60 g of a trifunctional aromatic isocyanate (Desmodur L75 K)

1.55 g of a polyol (Desmophen 800)

3.00 g of methyl ethyl ketone

Lacquer II (combination lacquer based on polyurethane/acrylic resin):

5 g G-Cure 105P70 (acrylic polyol resin)

1.17 g of a trifunctional aliphatic isocyanate (Desmodur N 100)

5.0 g of methyl ethyl ketone

Additive (I) in the Form of the Co or Fe Salt of an Unsaturated EtherCarboxylic Acid for "Test 3":

231.4 g of HD Ocenol 150/170×10 EO ether carboxylic acid are reactedwith 24.9 g of Co(II) acetate×4H₂ O (dissolved in 80 ml of H₂ O) in 150ml of xylene with elimination of water and acetic acid. A water-solubleCo soap is obtained. The Fe soap is prepared in the same way. Theadditives thus prepared were used in Examples 51 and 52.

The ether carboxylic acid used was conventionally prepared as follows:10 moles of ethylene oxide were added to the unsaturated fatty alcoholHD Ocenol 150/170 (definition see above). The adduct was converted intoits Na salt with NaOH and then reacted with chloroacetic acid to formthe ether carboxylic acid.

What is claimed is:
 1. A process for permanently improving surfaces ofpolyolefin-based moldings and films for bonding with coatings andadhesives, comprising the steps of:(a) molding a composition comprisingat least one polyolefin, about 0.01 to about 10% by weight, based on thepolyolefin of at least one migratable, crosslinkable amphiphile compoundcontaining at least one substituent of high polarity in an otherwisehydrocarbon-based basic molecule having a molecular weight of about 50to about 5,000 Dalton and a catalytically effective amount of a catalystwhich promotes crosslinking of the crosslinkable amphiphile compound inthe plastic surface to form a polyolefin-based molding or film; (b)allowing said crosslinkable amphiphile compound to migrate to thesurface of said polyolefin-based molding or film and crosslink.
 2. Theprocess claimed in claim 1, wherein a tensile shear strength of at leastabout 1.2 N/mm² is obtained when a polyurethane adhesive is applied to asurface of said polyolefin-based molding or film, as determined on aZwick Universal testing machine at test speeds of 15 mm/min.
 3. Theprocess of claim 1, wherein the at least one migratable amphiphilecompound has an iodine value of about 10 to about
 200. 4. The process ofclaim 1, wherein the at least one migratable amphiphile compoundsubstituent of high polarity comprises a group selected from the groupconsisting of carboxyl, hydroxyl, amino, oxazoline, epoxy, isocyanateand mixtures thereof.
 5. The process of claim 1, wherein the catalystcomprises a transition metal and the transition metal content of thepolyolefin molding or film is less than 5 ppm.
 6. The process of claim5, wherein the transition metals comprise salts of carboxylic acids. 7.The process of claim 1, wherein the transition metal content of thepolyolefin, molding or film is less than about 1 ppm.
 8. Apolyolefin-based molding or film comprising a surface, produced by theprocess of claim
 1. 9. The process of claim 1, wherein the migratableamphiphile compound is oleophilic and comprises olefinically unsaturatedhydrocarbon residues that have a linear, branced and/or cyclic structureand are liquid at room temperature.
 10. The process of claim 1, whereinthe migratable, crosslinkable, amphiphile compound comprises a groupcontaining a hetero atom as the substituent of high polarity.
 11. Theprocess of claim 10, wherein the hetero atom is selected from the groupconsisting of O,N, halogen and mixtures thereof.
 12. The process ofclaim 1, wherein the quantities of catalyst used are limited to such anextent that there is no degradation of the polyolefin after 14 days inan atmosphere of at least about 80% relative humidity at a temperatureof 60° C.
 13. The process of claim 1, wherein the migratable amphiphilecompound is a mixture of monounsaturated carboxylic acid and at leastabout 50% polyolefinically unsaturated carboxylic acid.
 14. The processof claim 13, wherein the carboxylic acids contain at least about 12carbon atoms.
 15. The process of claim 1, wherein the migratableamphiphile compound comprises olefinic double bonds.
 16. The process ofclaim 1, wherein the migratable amphiphile compound is liquid at roomtemperature.
 17. The process of claim 1, wherein the migratableamphiphile compound comprises branched hydrocarbon residues.
 18. Theprocess of claim 17, wherein the branched hydrocarbon residues comprisetertiary carbon atoms.
 19. The process of claim 1, wherein themigratable amphiphile compound comprises multiple olefinic double bonds.